growth performance and proximate composition of mixed cultures of marine microalgae (nannochloropsis sp. & tetraselmis sp.) with monocultures

The growth performance and proximate composition of two marine microalgae, Nannochloropsis sp. and Tetraselmis sp., in monoculture and mixed culture of both species under laboratory conditions were compared. Microalgae were cultured in enriched seawater (28 ppt) in 8 L plastic bottles using Conway medium. Microalgae were grown in a temperature-controlled room (25°C) under continuous illumination at a light intensity of about 3,000 Lux for 240 hours (10 days). Results showed that maximum cell density and growth rate of both species (45.06±2.67×105 cells ml-1 and 0.43±0.02 day-1, reps.) in mixed culture had a significantly higher than Tetraselmis sp. (5.09±0.99×105 cells ml-1 and 0.16±0.03 day-1, reps.), but not significantly different with Nannochloropsis sp. (29.25±22.70×105 cells ml-1 and 0.37±0.14 day-1, reps.) in monoculture. For proximate composition, protein content of both species in mixed culture and Nannochloropsis sp. in monoculture was significantly higher than for Tetraselmis sp. in monoculture after 120 and 240 hours of cultivation. Carbohydrate and lipid contents of each treatment were found to be significantly different after 120 hours of cultivation but not significantly different after 240 hours of cultivation. Therefore, this study indicates that an alternative option for commercial microalgal production is to use a mixed culture to obtain higher production.